The present invention relates generally to medical devices and in particular aspects to tissue graft devices that are comprised of extracellular matrix material layers having properties that differ from one another.
As further background, when tissue is damaged or otherwise disrupted, whether by disease, by trauma including surgery, or in any other manner, a series of interdependent physiological events occur that result in tissue repair. These events occur within (or are otherwise associated with) what are generally believed to be the four major phases of healing: inflammation, cell proliferation, matrix deposition, and remodeling. Tissue wound healing is a dynamic, complex process that involves the integrated action of several body components such as but not limited to extracellular matrix materials, various cell types, and soluble mediators (i.e., cytokines and growth factors).
Dermal wound healing is especially critical to maintaining the body's primary line of defense. The skin provides the body with a protective barrier from, among other things, chemical and mechanical challenges, harmful pathogens, and ultraviolet radiation. Chronic wounds compromise the skin's ability to defend against these agents, due to the prolonged wound healing process. For chronic wounds, the body is unable to complete the wound healing process due to a compromised vascular and/or immune system. Without clinical intervention, these chronic wounds can lead to the spread of infection, significant necrotic tissue, and other bodily problems including possible amputation in the case of ulcers in the foot. Advanced states of chronic dermal wounds present a significant clinical challenge. In the United States alone, there are over 3 million cases of chronic wounds annually.
A variety of medical graft products have been developed for treating cutaneous, intracutaneous, and subcutaneous tissues. Likewise, a variety of materials have been used to form these products, including collagenous materials. Suitable collagenous materials can be provided by collagenous extracellular matrix (ECM) materials. Such ECM materials can be provided, for example, by materials isolated from a suitable tissue source from a warm-blooded vertebrate, e.g., from the submucosal tissue of a mammal. Such isolated submucosal tissue, for example, small intestinal submucosa (SIS), can be processed so as to have bioremodelable properties and promote cellular invasion and ingrowth. Illustratively, sheet-form SIS material has been used as a surgical graft to provide tissue support in patients, e.g., in hernia repair operations. In some forms, the sheet-form SIS material includes a multilayered configuration to provide strength, reinforcement, and/or other enhancements to the graft.
There remain needs for improved and/or alternative tissue graft devices, as well as methods for forming and utilizing the same. The present invention is addressed to those needs.